High power battery systems are often composed of a multitude of individual electro-chemical cells that are linked together in a combination of series and parallel connections to generate an overall battery system that has the appropriate voltage, current and energy storage characteristics for the application.
Large battery systems are often broken down into smaller modules for ease of handling, monitoring and replacement. Each individual module will usually include electronics for maintaining the health, charge balance and monitoring of the cells within that module.
For lower power systems, each module may include power control switches that can be used to enable and disable current flow through the module. Monitoring of the amount of current flow may also be provided. For high power systems, the power control switches would be too large and expensive to place inside each module. In these cases, modules placed in series would have current switching and monitoring electronics in one place in series with the entire string of modules. If parallel connection of modules is required to increase energy storage or peak power available, such parallel connections are either done between separate strings of modules, or they are combined tying groups of modules in parallel and then in series.
While the concepts outlined above generally outline the concepts of modular battery systems used in high power situations, the above systems fail to consider how ageing battery packs, and the inclusion of dissimilar capacity modules can adversely affect the safety and performance of the entire energy storage system.
There remains a need for modular energy storage system that will allow a variety of modules to be placed together to form a solution of arbitrary voltage, capacity and power, without the need to laboriously match every module in the system to each other.